Author:
T Arai1*, H Takahashi1, Y Kusuya1, H Majima1,2, A Watanabe1, K Kamei1
Author address:
1Medical Mycology Research Center, Chiba University, Chiba, Japan
2Department of Respiratory Medicine, Tokyo Medical and Dental University, Tokyo, Japan
Full conference title:
10th Advances Against Aspergillosis and Mucormycosis
Date: 2 February 2022
Abstract:
Purpose:
The most studied azole-resistant mechanism of Aspergillus fumigatus is decreased affinity of the drug for Cyp51A, the drug target molecule, due to its amino acid substitutions. Typically, each azole resistance caused by the designated amino acid substitution of Cyp51A has a specific pattern depending on the substitution site. However, different azole susceptibility patterns have been reported even among the strains possessing the same mutation in Cyp51A. In this way, the overall picture of molecular mechanisms inducing azole resistance remains unclear. This study reports a novel factor that has been shown to contribute additively to azole resistance in collaboration with the Cyp51A mutation.
Methods:
Comparative genomic analysis was performed among the strains with the same cyp51A mutation isolated from the same patient but with different azole resistance patterns. To investigate the association between the novel mutation and azole resistance, the mutant allele was replaced with the wild-type allele by the CRISPR-Cas9 system. Antifungal susceptibility tests were performed according to the CLSI-M38.
Results:
A. fumigatus strains serially isolated from a patient with interstitial pneumonia were analyzed. The MICs of isolate in 2014 were ITCZ=2 and VRCZ> 8, whereas the ones of isolate in 2015 were ITCZ=8 and VRCZ> 8. The numbers of short tandem repeats of these two strains are identical, and same mutation (G448S) in cyp51A was confirmed. As a result of genome comparison analysis between these two strains, the mutation was found in the gene encoding insulin-induced protein (Insig) of the multiazole-resistant strain. Replacing the mutated insig gene of this strain with the wild-type gene restored susceptibility to ITCZ. On the other hand, the replacing the wild-type insig gene in a laboratory strain Afs35 with the mutation insig gene did not change the susceptibility to ITCZ and VRCZ.
Conclusion:
This study confirmed the novel genetic changes related to azole resistance. The Insig mutation contributes additively to azole resistance in collaboration with the Cyp51A mutation but does not alone itself. Our results indicate that focusing on the phenotypes of multiple genes is essential to clarify the overall picture of the azole resistance mechanism of A. fumigatus.
Abstract Number: 68
Conference Year: 2022
Link to conference website: https://aaam2022.org/
URL Conference abstract: